21320416 has 48 divisors (see below), whose sum is σ = 46103904. Its totient is φ = 9644544.

The previous prime is 21320407. The next prime is 21320447. The reversal of 21320416 is 61402312.

It is a junction number, because it is equal to n+sod(n) for n = 21320393 and 21320402.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 21565 + ... + 22531.

It is an arithmetic number, because the mean of its divisors is an integer number (960498).

Almost surely, 2^21320416 is an apocalyptic number.

21320416 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21320416, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23051952).

21320416 is an abundant number, since it is smaller than the sum of its proper divisors (24783488).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21320416 is a wasteful number, since it uses less digits than its factorization.

21320416 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1043 (or 1035 counting only the distinct ones).

The product of its (nonzero) digits is 288, while the sum is 19.

The square root of 21320416 is about 4617.4035994268. The cubic root of 21320416 is about 277.2885210715.

Adding to 21320416 its reverse (61402312), we get a palindrome (82722728).

It can be divided in two parts, 21320 and 416, that added together give a triangular number (21736 = T₂₀₈).

The spelling of 21320416 in words is "twenty-one million, three hundred twenty thousand, four hundred sixteen".